1. Field of the Invention
The present invention pertains to the fields of stock materials and antistatic fibers. The present invention relates to stock materials which are strands, the strands being impregnated with free carbon (i.e. conductive carbon black particles), these impregnated strands being used as antistatic textiles. More specifically, the present invention pertains to an antistatic textile yarn which is strengthened by being solvent bonded to a support yarn.
2. Description of the Prior Art
Several U.S. patents are related to the general area within which the present invention is located. However, applicants do not believe that any of these patents cover the process or products of the present invention. The closest prior art known to applicants includes the following U.S. Pat. Nos. 4,255,487; 3,823,035; 3,647,591; 4,107,914; 3,945,186; 3,206,923; 3,291,897. The relationship between the present invention and each of these patents is discussed below.
U.S. Pat. No. 4,225,487 and U.S. Pat. No. 3,823,035, to Sanders, disclose a process of suffusing conductive carbon black particles into a polymeric substrate. The Sanders patents do not refer to any process for supporting conductive strands with nonconductive strands. The Sanders patents do, however, disclose a process which forms a very important part of the process of the present invention. The present invention is an improvement on the Sanders patents in the instances in which a conductive strand subsequently undergoes the downstream process operations of warping, weaving, knitting, etc. The present invention requires additional process steps over those steps described in both Sanders patents. Both Sanders patents are hereby incorporated by reference.
U.S Pat. No. 3,657,591 discloses a process for making acid bonded nonwoven fabrics. In this patent a nonwoven fabric containing a blend of staple fibers is contacted by an acid which softens only a specific type of fiber in the blend, after which the blend is compressed in order to bond the fibers together. In contrast, the instant invention does not involve the use of any pressure in order to achieve bonding.
U.S. Pat. No. 4,107,914 discloses a process for making a twistless staple yarn by bonding staple fiber together through the use of a solvent. The process described in U.S. Pat. No. 4,107,914 requires that ". . . the fiber strand is . . . bonded by bringing it in direct contact with a heated surface, e.g. a drum." In constrast, the method of the instant invention applies conductive mix to a substrate filament, and the filament, while wet with mix, is allowed to contact nothing but the atmosphere and the support yarn. Contact with any other object (e.g. a guide or drum) will result in the accumulation of excessive conductive mix on the object. The accumulation of conductive mix on an object, if dislodged onto the yarn, will cause a serious yarn and/or package defect.
U.S. Pat. No. 3,945,186 discloses a process of manufacturing a twistless (or low twist) staple fiber yarn, the yarn being made coherent by the addition of heated acid after a continuous filament yarn is added to staple fiber material. The process disclosed in U.S. Pat. No. 3,945,186 differs from the instant invention in that the process of making the supported antistatic yarn of the instant invention involves applying solvent to only the filamentary substrate (not the support yarn) followed by bringing the substrate and the support yarn together. This is to be contrasted with U.S. Pat. No. 3,945,186 which first brings both yarns together and then applies solvent to both yarns to achieve a bonding. It was unexpected (in the instant invention) that the application of solvent to only one of the yarns would permit bonding between the yarns to occur.
U.S. Pat. Nos. 3,291,897 and 3,206,923 both disclose twisted products which resemble the instant specification only remotely, in that they both provide a very different way of achieving the advantages of the present invention.